Python3新手求助：loop()运行后无法接收新输入并应用到函数

Hey there! Congrats on building your first app after 3 weeks of learning— that's awesome! Let's figure out why your loop isn't updating with new inputs and get it working right.

The Core Problems in Your Code #

Let's break down the main issues first:

• Variable Scope: Your amount and rate variables are defined globally, but when you redefine them inside loop(), they're local to that function. Functions like tot_with_tax() still use the original global values instead of the new ones you enter.
• Misplaced Function Calls & Returns: The line return in_page(), tot_with_tax_exit(), print(tot_with_tax()), loop() in loop() calls all these functions at once, creating messy execution flow. Recursively returning loop() also isn't the cleanest way to handle repetition here.
• Unreliable Exit Check: tot_with_tax_exit() relies on the global amount, so it won't see the new values you enter in the loop, and the int(0) check is unnecessary (just compare to 0 directly).

Fixed Version of Your Code #

Here's a revised version that addresses all these issues:

from os import sys

def say_bye():
    print("GoodBye!")
    sys.exit()

def loop():
    while True:
        print("\nWould you like to enter another value?")
        choice2 = input('y/n: ')
        if choice2.lower() == 'y':
            print()
            amount = float(input("enter another price: "))
            # Check exit condition right after entering amount
            if amount == 0:
                print('\nWould you like to exit?')
                choice = input('y/n?: ')
                if choice.lower() == 'y':
                    say_bye()
                else:
                    # Skip to next iteration to let user re-enter
                    continue
            rate = float(input("tax rate: "))
            calculate_and_print_total(amount, rate)
        else:
            say_bye()

def calculate_and_print_total(amount, rate):
    tax = amount * rate
    total = tax + amount
    print(f"\nYour total after tax is: {total}")

def welcome_page():
    print("\nWelcome to the tax tool!")
    print("\nPlease enter your total price, and tax rate.")

# Initial setup
welcome_page()
initial_amount = float(input("enter price: "))
if initial_amount == 0:
    print('\nWould you like to exit?')
    initial_choice = input('y/n?: ')
    if initial_choice.lower() == 'y':
        say_bye()
initial_rate = float(input("tax rate: "))
calculate_and_print_total(initial_amount, initial_rate)

# Start the loop
loop()

Key Changes Explained #

• No More Global Variables: We pass amount and rate as parameters to calculate_and_print_total() so every new input is used directly, eliminating confusion between global and local values.
• Cleaner Loop Logic: Replaced the recursive loop() call with a while True loop, which is easier to follow and avoids potential stack overflow issues with deep recursion.
• Simplified Exit Check: Moved the "exit if amount is 0" logic directly into the input flow, so it checks the new value immediately instead of relying on a separate function that can't access local variables.
• Renamed Functions for Clarity: in_page() → welcome_page() and combined tot_with_tax()/tot_with_tax_exit() into calculate_and_print_total() to make the code more readable.
• Case Insensitivity: Added .lower() to input checks so users can enter 'Y' or 'N' too, making the tool more user-friendly.

Give this a try— it should now accept new inputs in the loop and calculate the correct total every time!

内容的提问来源于stack exchange，提问作者AFK Aaron